The present invention relates to an apparatus for a tenter frame for drying a web of knitted material, the tenter frame being of the type having a feed roller for feeding the web along a feed path through a pair of opposed finger assemblies for smoothing the edges of the fabric to a pair of endless belts having vertical needles for securing the web during transport through a drying chamber.
In the handling of knitted fabric in a tenter frame, a fabric web is fed along a path to ultimately pass through a drying chamber in which the web is dried. To ensure that the web is of uniform width and generally planar during its travel through the drying chamber, the lengthwise edges of the web are pressed onto a plurality of uniformly spaced, upright pins mounted on a pair of spaced apart endless belt assemblies which extend into and through the drying chamber. The assemblies on which the respective rollers and endless belts forming the nip are mounted are pivotably adjustable to accommodate changes in web width, which pivoting causes relative movement of the assemblies with respect to the feed roller. To ensure that the web maintains its width as it is fed into the nip in which a pair of spaced pin rollers press the web border onto the pins, a series of opposed fingers smooth the respective lengthwise borders of the web. The pair of endless belts then transport the web in generally flat disposition through the drying chamber.
The tenter frame is often provided with a support belt of the endless belt type running parallel to the feed path and positioned just below the web of knitted material for supporting the web during its travel so that sagging, which is detrimental, is avoided. The support belt extends from the feed roller to a position adjacent the nip. The support belt is driven by the feed roller so the belt travels in sychronization with the feed of the web.
Since the support belt is driven by the feed roller, it travels in synchronization with the rate of feed of the web into the drying chamber. However, problems arise in maintaining the synchronization of the support belt with the web since the distance between the feed roller and the nip region varies as the endless belt assemblies are pivoted to accommodate changes in the width of the web and this causes corresponding changes in the tension of the support belt since it is coupled to the feed roller. Additionally, the relative distance between the feed roller and the nip may change as the endless belt assemblies expand due to heat during operation and this change of position, in turn, creates a change in the distance between the feed roller and the nip regions. Accordingly, practical difficulties are encountered in maintaining the support belt at a suitable tension while driving the belt in synchronization with the rate of feed of the web.